Replication systems typically protect a primary data storage system (often called a production system or production site) by replicating the primary data storage system on a secondary data storage system (often called a replica system or replica site). The production site and the replica site are typically coupled by a communications network such as a wide area network (WAN).
A journal of a file system is a data structure that tracks or logs changes to or other activity in a file system, such as, for example, a file system of a production site. In the event of a system crash, or corruption of a file system due to, for example improper shutdown or startup procedures, hardware failures, and/or Network File System (NFS) write errors, the file system can be restored and/or inconsistencies repaired by reference to the journal. For example, a journal can be reviewed to find uncommitted transactions and a file system can be rolled back in time to changes made prior to these transactions. File system journals may keep track of one or more of stored metadata, stored data and related metadata.